Electric rotary machine and power generation systems using the same

ABSTRACT

The present invention provides an electric rotary machine including a rotor having a field magnet provided on a shaft, the field magnet comprising a first field magnet with magnetic poles of sequentially different polarities arranged in a rotational direction, a second field magnet with magnetic poles of sequentially different polarities arranged in a rotational direction wherein the second field magnet is rotatable on the shaft and displaced axially with respect to the first field magnet.

FIELD OF THE INVENTION

[0001] The present invention relates to an electric rotary machine usinga magnet for a field, and particularly, to an electric rotary machinefor a power generation system and a control method thereof.

DISCUSSION OF THE RELATED ART

[0002] In a conventional permanent magnet electric rotary machine, aninductive electromotive force E is determined by a constant magneticflux Φ generated by a permanent magnet arranged in a rotor and arotating angular velocity ω of an electric rotary machine. Specifically,when the rotating angular velocity ω (rotating speed) of the electricrotary machine increases, the inductive electromotive force of theelectric rotary machine rises in proportion thereto. Hence, operation ina high rotation region is difficult. Conventionally, operation in thehigh speed was made possible by the field weakening control technique.

[0003] But, this technique has drawbacks due to the heat generation by afield weakening current and lowered efficiency.

[0004] In a prior art method, a mechanism making use of a centrifugalforce using a spring and a governor, as a field weakening method ofmagnetic flux generated by a permanent magnet is utilized.

[0005] Also, the construction of a spring and a governor is complex andcostly.

SUMMARY OF THE INVENTION

[0006] The present invention provides an electric rotary machine whichallows ease of fabrication and enables a field weakening of magneticflux generated by a permanent magnet. Further, the present inventionprovides a power generation system provided with a permanent magnet typeelectric rotary machine capable of obtaining high torque characteristicsin a low rotation region, such as start of a heat engine, and highoutput power generation characteristics in a high rotation region.

[0007] In an object of the present invention an electric rotary machineincluding a rotor having a field magnet provided on a shaft is providedthe field magnet comprising a first field magnet with magnetic poles ofsequentially different polarities arranged in a rotational direction, asecond field magnet with magnetic poles of sequentially differentpolarities arranged in a rotational direction and the second fieldmagnet is rotatable on the shaft and displaced axially with respect tothe first field magnet.

[0008] In another object of the present invention an electric rotarymachine including a rotor having a field magnet provided on a shaft isprovided the field magnet comprising a first field magnet with magneticpoles of sequentially different polarities arranged in a rotationaldirection, a second field magnet with magnetic poles of sequentiallydifferent polarities arranged in a rotational direction wherein thesecond field magnet is rotatable on the shaft and displaced axially withrespect to the first field magnet and a composite magnetic field createdby the field magnets is changed.

[0009] In yet another object of the present invention a power generationsystem and a turbine power generation system is provided utilizing theelectric rotary machine of the present invention. Further, a method ofcontrolling a field magnet in a electric rotary machine is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The above advantages and features of the invention will be moreclearly understood from the following detailed description which isprovided in connection with the accompanying drawings.

[0011]FIG. 1 illustrates an electric rotary machine and a turbineaccording to one embodiment of the present invention;

[0012]FIG. 2 illustrates the electric rotary machine of FIG. 1;

[0013]FIG. 3 illustrates the same magnetic poles of rotors of theelectric rotary machine of FIG. 1 aligned on their center axes;

[0014]FIG. 4 illustrates the same magnetic poles of rotors of theelectric rotary machine of FIG. 1 deviated on their center axes;

[0015]FIGS. 5A and 5B illustrates characteristics of the electric rotarymachine of FIG. 1 according to the rotating angular velocity;

[0016]FIG. 6 is a control block diagram of the electric rotary machineof FIG. 1;

[0017]FIG. 7 illustrates an electric rotary machine in a state where anactuator is OFF according to a further embodiment of the presentinvention;

[0018]FIG. 8 illustrates an electric rotary machine in a state where anactuator is ON according to a further embodiment of the presentinvention;

[0019]FIG. 9 illustrates the inside of a rotor of an electric rotarymachine according to a further embodiment of the present invention;

[0020]FIG. 10 illustrates the inside of a rotor of an electric rotarymachine according to another embodiment of the present invention;

[0021]FIG. 11 illustrates an electric rotary machine in a state where anactuator is ON according to another embodiment of the present invention;

[0022]FIG. 12 illustrates a rotor of an electric rotary machineaccording to another embodiment of the present invention;

[0023]FIG. 13 illustrates a measurement of axial displacement of anelectric rotary machine according to another embodiment of the presentinvention;

[0024]FIG. 14 illustrates a rotor of an electric rotary machineaccording to another embodiment of the present invention; and

[0025]FIG. 15 illustrates a rotor of an electric rotary machineaccording to still another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0026] Exemplary embodiment of the present invention will be describedbelow in connection with the drawings. Other embodiments may be utilizedand structural or logical changes may be made without departing from thespirit or scope of the present invention. Like items are referred to bylike reference numerals throughout the drawings.

[0027] Referring now to the drawings, FIG. 1 comprises a compressor 90and a turbine 91 mounted directly or indirectly on an electric rotarymachine 2, a power converter 4 for controlling power of the electricrotary machine, a combustor 92, and a heat exchanger 93. While intakeair passes through the electric rotary machine 2 and flows to thecompressor 90 through a filter 96, it is noted that the construction maybe employed in which air is taken in between the electric rotary machine2 and the compressor 90. Further, in this embodiment, a waste heatrecovery device 94 is mounted to improve the efficiency of the wholepower generation system.

[0028] The permanent magnet type electric rotary machine 2 according tothe present embodiment is able to start the turbine 91. In starting theturbine, when the turbine is increased in speed from 0 to aself-sustaining speed, the electric rotary machine is operated as anelectric motor. The resistance torque increases rapidly as rotationstarts, decreases at 15 to 20% of the rated speed (Ng), and assumes zeroat 30 to 40% of the rated speed. The self-sustaining speed is about halfof the normal operating speed of the turbine, and if the former isreached, it is a speed such that the turbine no longer requiresassistance (torque of a motor) of a start device to assume a completedrive system, being operated as a power generator.

[0029] In FIG. 2, a stator core 10 is wound with an armature winding 11within a slot and connected to a housing 13 having a cooling passage 12through which a coolant flows. A permanent magnet recessed type rotor 20comprises a first rotor 20A secured to a shaft 22, and a second rotor20B separated from the shaft 22. Note, an interior permanent magnet typeor a surface magnet type rotor may be used. The first rotor 20A has apermanent magnet 21A provided with magnetic poles of sequentiallydifferent polarities in a rotational direction. Likewise, the secondrotor 20B has a permanent magnet 21B provided with magnetic poles ofsequentially different polarities in a rotational direction. A fieldmagnet in which a first field magnet and two rotors of the second rotorare arranged on the same shaft are opposed to the stator magnetic pole.

[0030] The inside diameter side of the second rotor 20B functions as anut part 23B, and a shaft threaded thereon functions as a tread (screw)part 23A of a bolt. Hence, the second rotor 20B is movable in an axialdirection while rotating relative to the shaft.

[0031] Further, a stopper is provided at a location apart from the sidesurface of the second rotor 20B so that the second rotor 20B may notprotrude exceeding a predetermined displacement or distance from thecenter of the stator. Further, if a stopper driving actuator 25 as aservo mechanism is provided so that the stopper 24 may be movedlaterally in parallel with the shaft, a value of deviation of the polecenter between the first field magnet and the second field magnet can bevaried. As a result, it is possible to control the whole effective orcomposite magnetic flux amount comprising the first field magnet and thesecond field magnet relative to the stator in which the armature winding11 is wound within the slot.

[0032] In the electric rotary machine in which fundamentally, thearmature winding is used for the stator and the permanent magnet is usedfor the rotor, if the rotational direction of the rotor when theelectric rotary machine functions as a motor is the same as that whenthe electric rotary machine functions as a power generator, thedirection of torque received by the rotor when the electric rotarymachine functions as a motor is opposite to that when the electricrotary machine functions as a power generator. If, if functions as amotor, the rotational direction of the rotor is opposite and thedirection of torque is also opposite. Likewise, if the electric rotarymachine functions as a power generator, the rotational direction of therotor is opposite and the direction of torque is also opposite.

[0033] Hence, the electric rotary machine functions as a motor in a lowrotational region as in the start of a turbine, the center of the poleof the first rotor 20A is aligned with that of the second rotor 20B, asshown in FIG. 3, to maximize the effective magnetic flux amount by thepermanent magnet opposite to the stator pole, thereby obtaining the hightorque characteristics. Then, when the electric rotary machine functionsas a power generator, when the rotational direction of the rotor is thesame as shown in FIG. 2, the torque direction received by the rotor isopposite to that when the electric rotary machine functions as a motor,and the center of the pole of the second rotor 20B is deviated whileincreasing the spacing between the first rotor 20A and the second rotor20B so as to disengage the nut part from the screw part relative to theshaft 22, thereby reducing the effective or composite magnetic fluxamount caused by the permanent magnet opposite to the stator magneticpole. In other word, there is a field weakening effect, and the highoutput generation characteristics are obtained in the high rotationalregion.

[0034]FIGS. 3 and 4 illustrate a relationship between a thread part 61of a bolt, a screw part 60 of a bolt, and a nut part 62. The thread part61 of a bolt and the nut part 62 correspond to the first rotor 20A andthe second rotor 20B, respectively. If the screw part 60 of a bolt(corresponding to 23A in FIG. 2) rotates in the same direction, the nutpart 62 is tightened or disengaged depending on the direction of torqueapplied to the nut part 62, and the second rotor 20B also functionssimilarly depending on the direction of torque of the rotor.

[0035]FIGS. 5A and 5B show the characteristics of the effective magneticflux relative to the rotating angular velocity of the permanent magnettype synchronous electric rotary machine, the inductive electromotiveforce, and the terminal voltage. The inductive electromotive force E ofthe permanent magnet type synchronous electric rotary machine isdetermined by the magnetic flux Φ generated by the permanent magnet andthe rotating angular velocity ω of the electric rotary machine. That is,as shown in FIG. 5A, if the magnetic flux Φ1 generated by the permanentmagnet arranged in the rotor is constant, when the rotating angularvelocity ω (rotating speed) increases, the inductive electromotive forceE1 of the electric rotary machine increases in proportion thereto.However, the power supply terminal voltage or capacity of the powerconverter 4 has a limit, and the inductive electromotive force generatedby the electric rotary machine has to be suppressed to a level lowerthan a certain condition. Therefore, the permanent magnet typesynchronous electric rotary machine must be subjected to the so-calledfield weakening control for reducing the magnetic flux generated by thepermanent magnet in a region in excess of a rotating speed.

[0036] Since the inductive electromotive force increases in proportionalto the rotating angular velocity, a current of the field weakeningcontrol has to be also increased. It is therefore necessary to introducea high current into a coil as a primary conductor, and heat generated bythe coil naturally increases. Therefore, there is the possibility thatefficiency is lowered and demagnetization of the permanent magnet inexcess of cooling ability occur caused by heat generation.

[0037] For example, as shown in FIG. 5A, when the magnetic flux Φ1generated by the permanent is changed to the magnetic flux Φ2 at a pointof the rotating angular velocity ω1 (rotating speed), a change occursfrom the inductive electromotive force E1 to the inductive electromotiveforce E2 of the electric rotary machine to enable limitation of themaximum value of the inductive electromotive force. FIG. 5B likewiseschematically shows the state when the magnetic flux Φ is finely changedaccording to the rotating angular velocity ω (rotating speed), theinductive electromotive force E can also be constantly maintained.

[0038] In the present invention, the rotor divided into the first fieldmagnet and the second field magnet of the electric rotary machine isarranged on the same shaft and the pole center of the first field magnetand the second field magnet is changed depending upon the direction ofthe rotational torque, in which when the electric rotary machinefunctions as a motor in a low rotation region as in the start of aturbine, the center of the magnetic poles of the first rotor and thesecond rotor are aligned to increase the effective magnetic flux amountcaused by the permanent magnet opposed to the stator magnetic pole, thusobtaining the high torque characteristics. Next, when the electricrotary machine functions as a power generator, when the rotationaldirection of the rotor is the same, the torque direction received by therotor is opposite to that when the electric rotary machine functions asa motor so that the center of the same magnetic pole of the first rotorand the second rotor is deviated to reduce the effective magnetic fluxamount caused by the permanent magnet opposite to the stator magneticpole. In other words, there is a field weakening effect, and the highoutput generation characteristics are obtained in a high rotationregion.

[0039] Further, as one embodiment of means for obtaining thecharacteristics shown in FIG. 5B, there can be used an electric rotarymachine in which the first field magnet is secured to the shaft, thesecond field magnet is connected movably to the shaft, the shaft has ascrew part of a bolt, and the second field magnet has a nut part on theinner peripheral side thereof, which are connected with a screwfunction, a stopper is provided at a location apart from the side of thesecond field magnet, and a servo mechanism in which the stopper isvariable in a parallel direction with the shaft according to therotating speed.

[0040] In FIG. 6, on the basis of information (such as compressorpressure, gas temperature, operating mode, and opening degree of athrottle for fuel gas) from a turbine controller and a sensor installedsingly, and the rotating speed of the permanent magnet type synchronouselectric rotary machine 2, an operation judgment part 101 judges theoperation of the permanent magnet type synchronous electric rotarymachine 2 to output a current instruction value. The current instructionvalue output from the operation judgment part 101 is input in a currentcontrol block 102 for carrying out non-interference control relative toa difference relative to the present current value of the permanentmagnet type synchronous electric rotary machine 2.

[0041] Output from the current control block 102 is converted into a3-phase AC by a rotation coordinate converter 103 to control thepermanent magnet type synchronous electric rotary machine 2 through aPWM inverter main circuit 104. Further, various phases of current (atleast a 2-phase current) and rotating speed (turbine rotating speed) ofthe permanent magnet type synchronous electric rotary machine 2 aredetected, and various phases of currents are converted into a biaxialcurrent by a biaxial conversion block 105 and fedback to a currentinstruction value. If there is a transmission, a value obtained bymultiplying the turbine rotating speed by two-fold may be used. Further,the rotating speed, the pole position or the like is detected by adetector 106 and fedback to various control blocks through the poleposition converter 107 and a speed converter 108.

[0042] While in the embodiment shown in FIG. 6, illustration is made ofa case where a position and speed sensor of the electric rotary machine2 and a current sensor of the electric rotary machine are present, it isnoted that even the control constitution of the type in which a part ofthese sensors is eliminated and the electric rotary machine 2 is drivenwithout a sensor, can be made. Further, in the permanent magnet typeelectric rotary machine according to the present invention, the centerof both poles of the first rotor and the second rotor may be aligned ordeviated depending on the operating state. Therefore, it has a functionfor correcting an advance of a current supply by a controller forcontrolling the power converter according to a deviation of a compositepole position of the first field magnet and the second field magnet.

[0043] In FIG. 13, a rotational angle θ and the axial displacementamount ΔL of the second rotor are in a proportional relation, and theaxial displacement amount ΔL is measured using a displacement measuringunit 64 and fedback to a controller of the power converter to obtain avalue exchanged to a deviation angle of the composite pole position ofthe first field magnet and the second field magnet, which is used foroptimum control for correcting an advance of a supply of current.

[0044] In FIG. 7, the first rotor 20A is secured to the shaft 22, thesecond rotor 20B is connected movably to the shaft 22 and a screw part23A of a bolt is secured to a part of the shaft. A sleeve 41 is securedto the inner peripheral side of the second field magnet, and a nut part23B is secured to the inside of the sleeve 41, which are integrated.Then the second rotor 20B rotates relative to the shaft 22 in adirection in which the nut part is disengaged from the screw part of abolt while enlarging a spacing between the first rotor 20A and thesecond rotor 20B.

[0045] When an interlinkage magnetic flux change occurs between theinner peripheral side of the second field magnet and the shaft 22 asrotation occurs due to the presence of a slight play or slack, there isa problem with electric corrosion. The sleeve 41 is formed ofnon-magnetic material which is higher in electric resistivity than iron,and thereby there is exhibited an effect that magnetic and electricalinsulation is provided between the inner peripheral side of the secondfield magnet and the shaft 22. Support mechanisms 40A and 40B areprovided internally of the sleeve 41 so that rotational motion,reciprocating motion and composite motion may be guided between thesecond field magnet and the shaft. In the second rotor 20B, a part ofthe shaft is provided with a screw part 23A of a bolt, and a function ofa screw is provided therewith and a movable stopper 24 is provided at alocation apart from the side of the second field magnet. Supportmechanisms 42 and 47 are provided between the stopper 24, the shaft andbetween the stopper 24 and the side surface of the second rotor 20B sothat rotational motion, reciprocating motion and composite motion may beguided. The support mechanism 42 has a function of a thrust bearing, andthe support mechanism 47 has a function for guiding rotational motion,reciprocating motion and composite motion while being a radial bearing.Further, with spring 48, the support mechanism 42 is allowed to enhanceits function as a trust bearing.

[0046] For the construction of the electromagnetic clutch, a coil 46 iswound about a yoke 44 and the stopper 24 may also serve as a function ofa movable core. The yoke 44 and the coil 46 are secured to a frame 49 ofthe electric rotary machine or to a part of a vehicle body (not shown),and a spring 45 is provided between the yoke 44 and the stopper 24 toprovide a function of a return device at energization cutoff. A bearing50 is provided between the frame 49 and the shaft 22 of the electricrotary machine for support.

[0047]FIG. 7 schematically shows the non-energizing state of the coil46, and FIG. 8 schematically shows the energizing state of the coil 46.When the coil 46 is energized, the yoke 44 becomes a powerfulelectromagnet to attract the stopper 24 which also functions as amovable iron. The electromagnetic clutch shown here is one example of aservo mechanism variable in parallel with the shaft, and a hydraulicactuator, a linear driving device using a rotary machine or a ballscrew, or a linear motor is used to enable fine locating of a stopper.

[0048]FIG. 9 shows one example of a sleeve 41 secured to the inside ofthe second rotor 20B. As one method for securing them, concavo-convexesare provided on a surface with which two parts of the second rotor 20Band the sleeve 41 come into contact. There is further shown a differenceof the inside of the first rotor 20A secured to the shaft 22 and thesecond rotor 20B separated from the shaft 22.

[0049] In FIG. 10, a recess part 53 is provided in the side surface ofthe first field magnet in which the first field magnet comes in contactwith the second field magnet, and a protrusion 54 which also functionsas the sleeve is provided on the second field magnet. The protrusion 54may be integrated with the sleeve 41 or may be integrated with thesecond rotor 20B. Thus, enough space can be secured for the sleeve 41and the spring 48, the support mechanisms 40A and 40B, and the nut part23B. This is an effective technique for the electric rotary machinehaving a thin axial laminated thickness of the second rotor 20B.

[0050] In FIG. 11, the basic elements shown in FIG. 11 are the same asthose of FIG. 7, but the electromagnetic clutch is modified. In FIG. 11,the coil 46 is in an energized state, and at the time of energizationcutoff, the yoke 44 is separated from the stopper 24 by the spring 45.The present embodiment obtains thrust by a screw function caused bymutual action of the screw part 23A in which torque is applied to thesecond rotor 20B and the nut part 23B. If thrust for extruding thestopper 24 due to the mutual relation between the screw and the torqueis applied, when the energization of the coil 46 is cutoff, the stopper24 is disengaged from the yoke 44. The yoke 44 is secured to the frame49 through an arm 52. The electromagnetic clutch shown in FIG. 11 is oneexample of a servo mechanism in which the stopper 24 is variable inparallel with the shaft similarly to the description of FIGS. 7 and 8,and a hydraulic actuator, a linear driving device using an electricrotary machine and a ball screw or a linear motor is used to enablefiner locating of the stopper.

[0051] In FIG. 12, the first rotor 20A is firmly secured to the shaft 22whereas the second rotor 20B has a freedom of movement with respect tothe shaft 22. Accordingly, there is a slight mechanical dimensional playbetween the second rotor 20B and the shaft 22, and when a large torqueor a centrifugal force is applied, the eccentricity may sometimes occur.Therefore, the air gap Gap2 between the second rotor 20B having thesecond field magnet and the stator is made larger than the air gap Gap1between the first rotor 20A having the first field magnet and thestator, thereby providing an effect of omitting a mechanical connectionbetween the second rotor 20B and the stator caused by the eccentricity.

[0052] In FIG. 15, the length of the inner peripheral side of the secondrotor 20B is made shorter than the outer peripheral side thereof, and astopper 24 and a servo mechanism 25 are provided internally of thesecond rotor 20B. Thus, restricting the axial length of the whole rotorcaused by the stopper 24 and the servo mechanism 25.

[0053] Hence, the present invention provides an electric rotary machineincluding a rotor having a field magnet provided on a shaft. The fieldmagnet comprising a first field magnet with magnetic poles ofsequentially different polarities arranged in a rotational direction, asecond field magnet with magnetic poles of sequentially differentpolarities arranged in a rotational direction and the second fieldmagnet is rotatable on the shaft and displaced axially with respect tothe first field magnet.

[0054] Although the invention has been described above in connectionwith exemplary embodiments, it is apparent that many modifications andsubstitutions can be made without departing from the spirit or scope ofthe invention. For example, although the present invention has beendescribed utilizing the 4-pole machine, the invention can also beapplied to a 2-pole, 6-pole or more machine. As one example, FIG. 14 isa schematic view of a stator of a permanent magnet type electric rotarymachine in a case where the present invention is applied to an 8-polemachine. Further, an interior permanent magnet type or a surface magnettype can be applied to the rotor. Accordingly, the invention is not tobe considered as limited by the foregoing description, but is onlylimited by the scope of the appended claims.

What is claimed as new and desired to be protected by Letters Patent ofthe United States is:
 1. An electric rotary machine including a rotorhaving a field magnet provided on a shaft, said field magnet comprising:a first field magnet with magnetic poles of sequentially differentpolarities arranged in a rotational direction; a second field magnetwith magnetic poles of sequentially different polarities arranged in arotational direction; and wherein said second field magnet is rotatableon said shaft and displaced axially with respect to said first fieldmagnet.
 2. The electric rotary machine of claim 1 wherein a compositemagnetic field created by said field magnets is changed.
 3. The electricrotary machine of claim 1 wherein said shaft has a screw part and saidsecond field magnet has a nut part provided on an inner peripheral sidethereof.
 4. The electric rotary machine of claim 1 further comprising astopper provided on said shaft at a predetermined distance away fromsaid second field magnet.
 5. The electric rotary machine of claim 4further comprising an actuator to vary said distance.
 6. The electricrotary machine of claim 1 wherein an axial displacement amount of saidsecond field magnet is detected and an advance of a current supply by acontroller for controlling a converter is corrected utilizing saiddisplacement amount.
 7. The electric rotary machine of claim 1 furthercomprising a plurality of support mechanism for guiding rotationalmotion, reciprocating motion and composite motion.
 8. The electricrotary machine of claim 1 wherein a sleeve is secured between an innerperipheral side of said second field magnet and the shaft.
 9. Theelectric rotary machine of claim 8 wherein said sleeve is formed of anon-magnetic material having an electrical resistivity at least higherthan that of iron.
 10. The electric rotary machine of claim 1 whereinsaid second field magnet is provided with a protrusion part and saidfirst field magnet is provided with a recess part for receiving saidprotrusion part.
 11. The electric rotary machine of claim 1 wherein anair gap between the rotor having said second field magnet and a statoris greater than that between the rotor having said first field magnetand said stator.
 12. An electric rotary machine including a rotor havinga field magnet provided on a shaft, said field magnet comprising: afirst field magnet with magnetic poles of sequentially differentpolarities arranged in a rotational direction; a second field magnetwith magnetic poles of sequentially different polarities arranged in arotational direction; and wherein said second field magnet is rotatableon said shaft and displaced axially with respect to said first fieldmagnet and a composite magnetic field created by said field magnets ischanged.
 13. The electric rotary machine of claim 12 wherein said shafthas a screw part and said second field magnet has a nut part provided onan inner peripheral side thereof.
 14. The electric rotary machine ofclaim 12 further comprising a stopper provided on said shaft at apredetermined distance away from said second field magnet.
 15. Theelectric rotary machine of claim 14 further comprising an actuator tovary said distance.
 16. The electric rotary machine of claim 12 whereinan axial displacement amount of said second field magnet is detected andan advance of a current supply by a controller for controlling aconverter is corrected utilizing said displacement amount.
 17. Theelectric rotary machine of claim 12 further comprising a plurality ofsupport mechanism for guiding rotational motion, reciprocating motionand composite motion.
 18. The electric rotary machine of claim 12wherein a sleeve is secured between an inner peripheral side of saidsecond field magnet and the shaft.
 19. The electric rotary machine ofclaim 18 wherein said sleeve is formed of a non-magnetic material havingan electrical resistivity at least higher than that of iron.
 20. Theelectric rotary machine of claim 12 wherein said second field magnet isprovided with a protrusion part and said first field magnet is providedwith a recess part for receiving said protrusion part.
 21. The electricrotary machine of claim 12 wherein an air gap between the rotor havingsaid second field magnet and a stator is greater than that between therotor having said first field magnet and said stator.
 22. An electricrotary machine including a rotor having a field magnet provided on ashaft, said field magnet comprising: a first field magnet with magneticpoles of sequentially different polarities arranged in a rotationaldirection; a second field magnet with magnetic poles of sequentiallydifferent polarities arranged in a rotational direction; and whereinsaid second field magnet is rotatable on said shaft and displacedaxially with respect to said first field magnet and a mechanism forchanging the composite magnetic field created is based on the directionof a torque of said with means for aligning the same magnetic poles ofsaid first field magnet and said second field magnet on their centeraxes by balancing the direction of said torque generated.
 23. A powergeneration system comprising an electric rotary machine including arotor having a field magnet provided on a shaft, said field magnetcomprising: a power converter for controlling power of said electricrotary machine; a heat engine; a first field magnet with magnetic polesof sequentially different polarities arranged in a rotational direction;a second field magnet with magnetic poles of sequentially differentpolarities arranged in a rotational direction; and wherein said secondfield magnet is rotatable on said shaft and displaced axially withrespect to said first field magnet.
 24. The power generation system ofclaim 23 wherein a composite magnetic field created by said fieldmagnets is changed.
 25. The power generation system of claim 23 whereinsaid shaft has a screw part and said second field magnet has a nut partprovided on an inner peripheral side thereof.
 26. The power generationsystem of claim 23 further comprising a stopper provided on said shaftat a predetermined distance away from said second field magnet.
 27. Thepower generation system of claim 26 further comprising an actuator tovary said distance.
 28. The power generation system of claim 23 whereinan axial displacement amount of said second field magnet is detected andan advance of a current supply by a controller for controlling aconverter is corrected utilizing said displacement amount.
 29. The powergeneration system of claim 23 further comprising a plurality of supportmechanism for guiding rotational motion, reciprocating motion andcomposite motion.
 30. The power generation system of claim 23 wherein asleeve is secured between an inner peripheral side of said second fieldmagnet and the shaft.
 31. The power generation system of claim 30wherein said sleeve is formed of a non-magnetic material having anelectrical resistivity at least higher than that of iron.
 32. The powergeneration system of claim 23 wherein said second field magnet isprovided with a protrusion part and said first field magnet is providedwith a recess part for receiving said protrusion part.
 33. The powergeneration system of claim 23 wherein an air gap between the rotorhaving said second field magnet and a stator is greater than thatbetween the rotor having said first field magnet and said stator.
 34. Apower generation system comprising an electric rotary machine includinga rotor having a field magnet provided on a shaft, said field magnetcomprising: a power converter for controlling power of said electricrotary machine; a heat engine; a first field magnet with magnetic polesof sequentially different polarities arranged in a rotational direction;a second field magnet with magnetic poles of sequentially differentpolarities arranged in a rotational direction; and wherein said secondfield magnet is rotatable on said shaft and displaced axially withrespect to said first field magnet and a composite magnetic fieldcreated by said field magnets is changed.
 35. The power generationsystem of claim 34 wherein said shaft has a screw part and said secondfield magnet has a nut part provided on an inner peripheral sidethereof.
 36. The power generation system of claim 34 further comprisinga stopper provided on said shaft at a predetermined distance away fromsaid second field magnet.
 37. The power generation system of claim 36further comprising an actuator to vary said distance.
 38. The powergeneration system of claim 34 wherein an axial displacement amount ofsaid second field magnet is detected and an advance of a current supplyby a controller for controlling a converter is corrected utilizing saiddisplacement amount.
 39. The power generation system of claim 34 furthercomprising a plurality of support mechanism for guiding rotationalmotion, reciprocating motion and composite motion.
 40. The powergeneration system of claim 34 wherein a sleeve is secured between aninner peripheral side of said second field magnet and the shaft.
 41. Thepower generation system of claim 40 wherein said sleeve is formed of anon-magnetic material having an electrical resistivity at least higherthan that of iron.
 42. The power generation system of claim 34 whereinsaid second field magnet is provided with a protrusion part and saidfirst field magnet is provided with a recess part for receiving saidprotrusion part.
 43. The power generation system of claim 34 wherein anair gap between the rotor having said second field magnet and a statoris greater than that between the rotor having said first field magnetand said stator.
 44. A turbine power generation system comprising anelectric rotary machine including a rotor having a field magnet providedon a shaft, said field magnet comprising: a power converter forcontrolling power of said electric rotary machine; a heat engine; acompressor; a turbine; a combustor; a first field magnet with magneticpoles of sequentially different polarities arranged in a rotationaldirection; a second field magnet with magnetic poles of sequentiallydifferent polarities arranged in a rotational direction; and whereinsaid second field magnet is rotatable on said shaft and displacedaxially with respect to said first field magnet.
 45. The powergeneration system of claim 44 wherein a composite magnetic field createdby said field magnets is changed.
 46. The turbine power generationsystem of claim 44 wherein said shaft has a screw part and said secondfield magnet has a nut part provided on an inner peripheral sidethereof.
 47. The turbine power generation system of claim 44 furthercomprising a stopper provided on said shaft at a predetermined distanceaway from said second field magnet.
 48. The turbine power generationsystem of claim 47 further comprising an actuator to vary said distance.49. The turbine power generation system of claim 44 wherein an axialdisplacement amount of said second field magnet is detected and anadvance of a current supply by a controller for controlling a converteris corrected utilizing said displacement amount.
 50. The turbine powergeneration system of claim 44 further comprising a plurality of supportmechanism for guiding rotational motion, reciprocating motion andcomposite motion.
 51. The turbine power generation system of claim 44wherein a sleeve is secured between an inner peripheral side of saidsecond field magnet and the shaft.
 52. The turbine power generationsystem of claim 51 wherein said sleeve is formed of a non-magneticmaterial having an electrical resistivity at least higher than that ofiron.
 53. The turbine power generation system of claim 44 wherein saidsecond field magnet is provided with a protrusion part and said firstfield magnet is provided with a recess part for receiving saidprotrusion part.
 54. The turbine power generation system of claim 44wherein an air gap between the rotor having said second field magnet anda stator is greater than that between the rotor having said first fieldmagnet and said stator.
 55. A turbine power generation system comprisingan electric rotary machine including a rotor having a field magnetprovided on a shaft, said field magnet comprising: a power converter forcontrolling power of said electric rotary machine; a heat engine; acompressor; a turbine; a combustor; a first field magnet with magneticpoles of sequentially different polarities arranged in a rotationaldirection; a second field magnet with magnetic poles of sequentiallydifferent polarities arranged in a rotational direction; and whereinsaid second field magnet is rotatable on said shaft and displacedaxially with respect to said first field magnet and a composite magneticfield created by said field magnets is changed.
 56. The turbine powergeneration system of claim 55 wherein said shaft has a screw part andsaid second field magnet has a nut part provided on an inner peripheralside thereof.
 57. The turbine power generation system of claim 55further comprising a stopper provided on said shaft at a predetermineddistance away from said second field magnet.
 58. The turbine powergeneration system of claim 57 further comprising an actuator to varysaid distance.
 59. The turbine power generation system of claim 55wherein an axial displacement amount of said second field magnet isdetected and an advance of a current supply by a controller forcontrolling a converter is corrected utilizing said displacement amount.60. The turbine power generation system of claim 55 further comprising aplurality of support mechanism for guiding rotational motion,reciprocating motion and composite motion.
 61. The turbine powergeneration system of claim 55 wherein a sleeve is secured between aninner peripheral side of said second field magnet and the shaft.
 62. Theturbine power generation system of claim 61 wherein said sleeve isformed of a non-magnetic material having an electrical resistivity atleast higher than that of iron.
 63. The turbine power generation systemof claim 55 wherein said second field magnet is provided with aprotrusion part and said first field magnet is provided with a recesspart for receiving said protrusion part.
 64. The turbine powergeneration system of claim 55 wherein an air gap between the rotorhaving said second field magnet and a stator is greater than thatbetween the rotor having said first field magnet and said stator.
 65. Amethod of controlling a magnetic field of an electric rotary machineincluding a rotor having a field magnet provided on a shaft, said methodcomprising the steps of: providing a first field magnet with magneticpoles of sequentially different polarities arranged in a rotationaldirection; providing a second field magnet with magnetic poles ofsequentially different polarities arranged in a rotational direction;and wherein said second field magnet is rotatable on said shaft anddisplaced axially with respect to said first field magnet.
 66. Themethod of claim 65 wherein a composite magnetic field created by saidfield magnets is changed.
 67. The method of claim 65 wherein said shafthas a screw part and said second field magnet has a nut part provided onan inner peripheral side thereof.
 68. The method of claim 65 furthercomprising a stopper provided on said shaft at a predetermined distanceaway from said second field magnet.
 69. The method of claim 68 furthercomprising an actuator to vary said distance.
 70. The method of claim 65wherein an axial displacement amount of said second field magnet isdetected and an advance of a current supply by a controller forcontrolling a converter is corrected utilizing said displacement amount.71. The method of claim 65 further comprising a plurality of supportmechanism for guiding rotational motion, reciprocating motion andcomposite motion.
 72. The method of claim 65 wherein a sleeve is securedbetween an inner peripheral side of said second field magnet and theshaft.
 73. The method of claim 72 wherein said sleeve is formed of anon-magnetic material having an electrical resistivity at least higherthan that of iron.
 74. The method of claim 65 wherein said second fieldmagnet is provided with a protrusion part and said first field magnet isprovided with a recess part for receiving said protrusion part.
 75. Themethod of claim 65 wherein an air gap between the rotor having saidsecond field magnet and a stator is greater than that between the rotorhaving said first field magnet and said stator.